# UEFN unusable, constant crash Assertion failed **URL:** \ **Category:** Issues and Bug Reporting\ **Tags:** closed, fortnite-creative, unreal-editor-for-fortnite, crash, bug-report, issue, fortnite\ **Created:** [February 24, 2026, 4:20pm UTC](https://forums.unrealengine.com/t/uefn-unusable-constant-crash-assertion-failed/2702010 "2026-02-24T16:20:23Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![AuraSV](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/aurasv/32/634912_2.png) [@AuraSV](https://forums.unrealengine.com/u/AuraSV)\ **Post date:** [February 24, 2026, 4:20pm UTC](https://forums.unrealengine.com/t/uefn-unusable-constant-crash-assertion-failed/2702010/1 "2026-02-24T16:20:23Z")
### Summary Assertion failed: (::DwmExtendFrameIntoClientArea(HWnd, &Margins)) \>= 0 File: WindowsWindow.cpp Line: 359 I’ve formated PC, reverted Driver updates but nothing helped. I keep getting this crash on UEFN, screen goes black and if i reopen UEFN without restarting PC the whole PC shuts down… If it helps I think it happens mostly when I alt tab or change windows. I got the logs saved but I don’t know where to send them. This only happens with UEFN. RX 6600 Ryzen 5 5600 32gb ram Windows 11 25H2 Hope someone can help me or that this can be fixed because its impossible to use UEFN like this. ### Please select what you are reporting on: Unreal Editor for Fortnite ### What Type of Bug are you experiencing? Stability ### Steps to Reproduce Open UEFN, use it, eventually it will crash. Seems to happen the most when you have Fortnite open and you keep altering between Fortnite and UEFN window. ### Expected Result It shouldn’t crash, you should be able to swap between apps without any problem. ### Observed Result Screen goes black, when it comes back crash report says Assertion failed: (::DwmExtendFrameIntoClientArea(HWnd, &Margins)) \>= 0 File: WindowsWindow.cpp Line: 359, then, if I don’t restart my PC, the whole pc will shut down if I reopen UEFN. ### Platform(s) PC ### Additional Notes I saw another person with this issue last month on this forum but he didn’t get any reply. ---
**Author:** ![AuraSV](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/aurasv/32/634912_2.png) [@AuraSV](https://forums.unrealengine.com/u/AuraSV)\ **Post date:** [February 25, 2026, 12:46am UTC](https://forums.unrealengine.com/t/uefn-unusable-constant-crash-assertion-failed/2702010/3 "2026-02-25T00:46:40Z")
Hi, I will keep you all updated as I find more stuff, this seems to happen way easier if you select an object on UEFN before alt tabing to Fortnite. Also it seems theres times it will crash when u alt tab to Fortnite even without UEFN. This crash doesn’t happen when alt tabing to other heavy games even if I select an object on UEFN before. Also logs here. [CrashReportClient.ini](https://forums.unrealengine.com/uploads/short-url/xg1cF3fnYKAa56zKwOm4xIxPKxA.ini) (160 Bytes) [EpicGamesLauncher.log](https://forums.unrealengine.com/uploads/short-url/rhKgJygDfJWaGXkZY91by8WOmAv.log) (106.0 KB) [UEMinidump.dmp](https://forums.unrealengine.com/uploads/short-url/igOT5YaqUxlvrR7gIAfvQK3S7JF.dmp) (587.3 KB) [CrashContext.runtime-xml](https://forums.unrealengine.com/uploads/short-url/herRPtc8SdSh01DutbnWdkMpFkK.runtime-xm) (25.0 KB) ---
**Author:** ![AuraSV](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/aurasv/32/634912_2.png) [@AuraSV](https://forums.unrealengine.com/u/AuraSV)\ **Post date:** [February 25, 2026, 12:55am UTC](https://forums.unrealengine.com/t/uefn-unusable-constant-crash-assertion-failed/2702010/4 "2026-02-25T00:55:34Z")
Ok so like, maybe clicking an object was just a coincidence, but it crashes \>\> 100% \<\< of the times I click to Cancel memory calculation and return to Fortnite, there haven’t been a time it didn’t crash like that. ![cooked](https://d3kjluh73b9h9o.cloudfront.net/original/4X/7/6/3/763226b28340c0f5b148369786b826a3e27d5f7c.png) ---
**Author:** ![AuraSV](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/aurasv/32/634912_2.png) [@AuraSV](https://forums.unrealengine.com/u/AuraSV)\ **Post date:** [February 25, 2026, 5:09pm UTC](https://forums.unrealengine.com/t/uefn-unusable-constant-crash-assertion-failed/2702010/5 "2026-02-25T17:09:19Z")
Ok, so a resume: It feels easier to crash when you select an object / cancel a mem calc / Fortnite is on a loading screen before switching from UEFN to Fortnite. But it feels random, I can’t really find a way to force crash the game. Loading screen one seems to be the easier way tho. ---
**Author:** ![AuraSV](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/aurasv/32/634912_2.png) [@AuraSV](https://forums.unrealengine.com/u/AuraSV)\ **Post date:** [February 25, 2026, 10:46pm UTC](https://forums.unrealengine.com/t/uefn-unusable-constant-crash-assertion-failed/2702010/6 "2026-02-25T22:46:04Z")
I FOUND THE ISSUE This only happens when Windows 11 Transparency effects are On! Disabling it stop the crashes but this should be looked at, a lot of people probably have it on. ---
**Author:** ![Flak](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/flak/32/769441_2.png) [@Flak](https://forums.unrealengine.com/u/Flak)\ **Post date:** [February 25, 2026, 11:14pm UTC](https://forums.unrealengine.com/t/uefn-unusable-constant-crash-assertion-failed/2702010/7 "2026-02-25T23:14:11Z")
Thank you so much for letting us know, Aura! ---
**Author:** ![Bug-Reporter](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/bug-reporter/32/997076_2.png) [@Bug-Reporter](https://forums.unrealengine.com/u/Bug-Reporter)\ **Post date:** [March 10, 2026, 7:00pm UTC](https://forums.unrealengine.com/t/uefn-unusable-constant-crash-assertion-failed/2702010/9 "2026-03-10T19:00:41Z")
FORT-1060673 has been ‘Closed’. We’re unable to reproduce this issue. ---
**Author:** ![Jimbohalo10](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/jimbohalo10/32/961440_2.png) [@Jimbohalo10](https://forums.unrealengine.com/u/Jimbohalo10)\ **Post date:** [May 16, 2026, 1:42pm UTC](https://forums.unrealengine.com/t/uefn-unusable-constant-crash-assertion-failed/2702010/10 "2026-05-16T13:42:19Z")
hi all, You may have to install a new latest Graphics driver. [RESOLVED: Known issues with NVIDIA 576.02 drivers on RTX 50-series GPUs | Epic Developer Community](https://dev.epicgames.com/community/learning/knowledge-base/pBjb/twinmotion-known-issues-with-nvidia-576-02-drivers-on-rtx-50-series-gpus) Looking at the log the Epic Games Launcher (EPGL) need to be uninstalled from Windows 11 using the uninstaller. Then get an authorised version from Epic EPGL and install using Run as Administrator from Windows 11 File Explorer delete the following directories C:\Users%USERNAME%\AppData\Local\FortniteGame C:\Users%USERNAME% \AppData\Local\D3DSCache C:\Users%USERNAME% \AppData\Local\FabPlugins C:\Users%USERNAME% \AppData\Local\Epic Games Restart the PC login using Email/password. Your current Epic Account is currently unable to update EPGL EOSOverlay so deleting re-installing may solve this. Recommend uninstall your current UEFN and Fortnite and UE5 standard if installed from inside the new EPGL, the reinstall UEFN/Fortnite You may have to install a new latest Graphics driver. ---
**Author:** ![system](https://d3kjluh73b9h9o.cloudfront.net/original/4X/7/1/3/713c9d3f58553f0de89543d76a8a3a2779dc9fa4.png) [@system](https://forums.unrealengine.com/u/system)\ **Post date:** [August 23, 2026, 4:20pm UTC](https://forums.unrealengine.com/t/uefn-unusable-constant-crash-assertion-failed/2702010/11 "2026-08-23T16:20:44Z")
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